Unsaturated copolymer resin
The unsaturated copolymer resin to be used in the present invention is known and can be prepared by copolymerizing an .alpha.-olefin having 2 to 12 carbon atoms with an aliphatic nonconjugated diene in the presence of a Ziegler-Natta catalyst. Examples of the unsaturated copolymer resin are disclosed in Japanese Laid-Open Patent Application Nos. 165907/80, 30413/81, 30414/81, 36508/81, 81 and 155416/84. These unsaturated copolymer resins are greatly improved over the conventional "polyolefinic resins" in terms of such aspects as crosslinkability, paintability and adhesive properties. However, the mechanical properties, thermal properties, solubility in organic solvent, miscibility with or dispersibility in dissimilar polymers and other properties of these unsaturated copolymer resins are essentially the same as those of the conventional polyolefinic resins.
Radical graft polymerization
The unsaturated copolymer resin composite of the present invention is prepared by radical graft polymerization and specific procedures of this polymerization are also known. One method consists of treating a blend of a polymer and a monomer with radiations such as .gamma.-rays and electron beams. In another method, a polymer is treated with radiations and subsequently reacted with a monomer. In still another method, a mixture of a polymer and a monomer either in solution, in a molten state or in a dispersion is subjected to graft polymerization in the presence of an organic or inorganic peroxide or a redox-system radical polymerization catalyst.
An illustrative method of grafting onto a polyolefinic resin consists of performing graft polymerization of a monomer in an aqueous dispersion or suspension in the presence of polypropylene particles [see, for example, Japanese Patent Publication No. 2346/74 and Japanese Laid-Open Patent Application No. 32990/77]. According to this method, the polypropylene is modified to have fairly satisfactorily properties but because of the use of an ordinary polypropylene as a raw polymer, the solubility of the final product in organic solvents is far from being satisfactory (see Comparative Example 1 to be described later in this specification).
Grafted polymers derived from unsaturated rubbers (e.g. natural rubber, polybutadiene, polyisoprene, polychloroprene and ethylene-propylene-diene terpolymer (EPDM)) are also known and are extensively used in practice as adhesives, primers and impact-resistant resins (e.g. impact-resistant polystyrene and acrylonitrile-butadiene-styrene (ABS) resin). The solubility of these graft polymers in organic solvents is in a satisfactory range but in order to increase their elastic modulus, the amount of the rubbers that are used as raw polymers must be limited.
An example of the reaction for grafting onto the unsaturated copolymer resin used in the present invention is disclosed in Japanese Laid-Open Patent Application No. 98508/82 filed by the applicants of subject application. According to the specification of this prior application, the adhesive properties of the unsaturated copolymer resin is greatly improved. However, the monomers that can be used are limited to unsaturated organic acids or derivatives thereof and their use is limited to less than 50 parts by weight per 100 parts by weight of the unsaturated copolymer resin. Therefore, the unsaturated copolymer resin modified by the method described in Japanese Laid-Open Patent Application No. 98508/82 is not anticipated to exhibit high performance in terms of such aspects as adhesion to or blending with styrenic resins or polyphenylene ether resins. Furthermore, because of the limited amount of monomers used, the modified unsaturated copolymer resin is also unsatisfactory in solubility in organic solvents and in miscibility with, or dispersibility in, dissimilar polymers.
As described above, the prior art is not considered to provide a successfully engineered technique for realizing enhanced utilization of unsaturated copolymer resins by greatly improving their solubility in organic solvents and their miscibility with, or dispersibility in, dissimilar polymers without substantially impairing the superior mechanical or thermal properties of the unsaturated copolymer resins which are inherent in polyolefinic resins.